鸟嘴式K形方管节点疲劳性能试验研究  

Experimental study on fatigue behaviors of bird-beak SHS K-joints

作　　者：程斌[1] 段英豪 黄凤华 Cheng Bin;Duan Yinghao;Huang Fenghua(Shanghai Jiao Tong University,Shanghai 200240,China)

机构地区：[1]上海交通大学,上海200240

出　　处：《土木工程学报》2021年第11期27-36,共10页China Civil Engineering Journal

基　　金：国家自然科学基金(51678359)。

摘　　要：为研究鸟嘴式K形方管节点的疲劳性能,设计制作8个节点试件开展支管面内受荷工况下的疲劳试验。首先对试件进行静力加载,通过二次外推法得到焊趾处的热点应力值和应力集中系数(SCF),探明此类节点的热点应力分布规律和敏感热点位置。在此基础上开展高周常幅疲劳荷载试验,重点研究节点的疲劳破坏模式、裂纹扩展规律、刚度退化性能以及特征疲劳寿命等。结果表明:方型鸟嘴式K形搭接节点的最大SCF位于支管搭接区,其他节点的最大SCF均位于冠部支管热点;疲劳裂纹萌生于SCF最大值位置,并在萌生后较短时间内扩展贯穿壁厚;疲劳裂纹贯穿壁厚之后的节点刚度退化明显,但累计刚度退化在10%以内;IIW和API规范的S-N曲线可用于常规壁厚的鸟嘴式节点疲劳寿命预测,其对薄壁鸟嘴式节点的适用性还有待验证。Eight specimens were fabricated and tested under cyclic brace in-plane force to investigate the fatigue behavior of bird-beak square hollow section(SHS)K-joints.Static loading was first implemented to obtain the hot spot stresses and stress concentration factors(SCFs)by employing quadratic extrapolation method,from which hot spot stress distributions and critical hot spots were revealed.During the subsequent high-cycle constant amplitude cyclic loading,the fatigue behaviors including fatigue failure mode,crack propagation features,rigidity degradation and characteristic fatigue life were all observed.The results show that the maximum SCFs of square bird-beak overlap K-joints always occur at the brace overlap areas,while the maximum SCFs of other joints commonly appear at the brace crown areas.The fatigue cracks were observed to initiate at the hot spots with the highest SCFs and to propagate through the plate thickness soon after initiation.Significant rigidity degradations happened after the crack run through the plate thickness,while the accumulated degradations were measured to be no greater than 10%.The S-N curves recommended by the codes of IIW and API for conventional SHS joints could also be used to predict the fatigue lives of bird-beak SHS K-joints with common thick walls,however,the applicability of the curves to the bird-beak K-joints composed of thin walls should be further validated.

关 键 词：方钢管 鸟嘴式节点 K形节点 热点应力 疲劳性能 

分 类 号：TU392.3[建筑科学—结构工程]